This invention relates to valves and more particularly to extreme temperature, high pressure, balanced, rising stem gate valves with super preloaded, stacked, solid lubricated metal-to-metal stem seals.
A non-rising stem gate valve with separable seats and automatic plastic sealed gate-seat and seat-body interfaces is disclosed in U.S. Pat. No. 2,433,638--Volpin. A similarly sealed valve of the rising stem, balanced type intended for high pressure use is disclosed in U.S. Pat. Nos. 3,538,938--Volpin, and 3,696,831--Fowler et al. In the latter two patents chevron stem packing compressed by annular screw plugs is employed for the stem seals.
A valve known as a "Graygate" appears to employ plural but separated metal-plastic-metal sandwich seals around the valve stem and in a bonnet pocket but the valve is of the non-rising stem type wherein the problem of an axially moving stem does not exist, the metal rings are not of the dished type, are not coined at their peripheries when in use.
It is believed that the valve of the present invention can be used without leakage in environments of higher pressure and over a wider temperature range than the valves discussed above.
Stacked dished packing rings for a pipe hanger are disclosed in U.S. Pat. No. 2,417,181--Sandilands, but here again there is no relative axial motion of the members being sealed, just a static seal, and the seal does not comprise rings of solid lubricant between dished metal rings that are flattened by the compression means, the latter appearing to be correlative in shape to that of the packing rings.
Difficulties experienced with dished metal-to-metal seal rings of the type disclosed in U.S. Pat. No. 2,992,840 to Reynolds et al are discussed in my aforementioned pending United States patent application Ser. No. 611,860 filed Sept. 10, 1975, now U.S. Pat. No. 4,056,272.
The tubing hanger seals disclosed in Ser. No. 611,860, now U.S. Pat. No. 4,056,272, are of various forms, including frusto conical metal rings flattened to some extent by compression means, but only a static seal is formed, there being no relative motion of hanger and well heat. In one embodiment (sold over a year prior hereto?) the seal is between an inner cylindrical surface and an outer conical surface; there is only one metal ring and no non-metallic ring; and the metal ring is rounded and coined on both its inner and outer peripheries adjacent its convex surface. Other embodiments disclosed in Ser. No. 611,860, now U.S. Pat. No. 4,056,272 application are believed not to have been offered for sale over a year prior hereto and also differ in various respects from the seal of the present application.